with \(M_N\) , \(M_K\) , and \(M_{K^\ast }\)  denoting the masses of \(N\) , \(K\) , and \(K^\ast \) , respectively. \(e\)  is the elementary charge unit and \(\hat{e}\)  stands for the charge operator acting on the nucleon field. \(\hat{\kappa }_N \equiv \kappa _p\hat{e} + \kappa _n(1-\hat{e})\)  with \(\kappa _p=1.793\)  being the anomalous magnetic moment of proton and \(\kappa _n=-1.913\)  the anomalous magnetic moment of neutron. The coupling constants \(g_{\gamma K K^{\ast }} = 0.413\)  and \(g_{\Lambda ^\ast NK} =4.20\)  are calculated from the decay width of \(\Gamma (K^{*\pm }\rightarrow K^{\pm }\gamma ) \approx 0.0503\)  MeV and \(\Gamma (\Lambda (1690)\rightarrow N\bar{K}) \approx 17.5\)  MeV, respectively, as given by RPP [1]}. The coupling \(g_{\Lambda ^\ast N K^\ast }\)  is treated as a free parameter to be determined by a fit to the data.
